Movable gripper for stretch film packaging machines

ABSTRACT

The upper jaw ( 12 ) of the gripper is provided posteriorly to the fulcrum shaft ( 10 ), with opposed portions ( 112′, 15 ) for the double effect cooperation with an eccentric ( 19 ) with a single eccentricity, keyed on the shaft ( 17 ) which controls the orientation of the same gripper. On the fulcrum shaft ( 10 ) of the jaws of the gripper, upon which there is fixed the arm ( 127 ) of the lower jaw ( 27 ) of the same gripper, there are assembled needle springs ( 29, 29 ′) suitably pre-loaded, which with one end are integral to said shaft and with the other end anchored to the posterior fork ( 112 ) of the arm of upper jaw ( 112 ), in such a manner to urge in closure the two jaws of the gripper with a correct pressure. The opening and closure movement of the gripper, in the phase of approach to the distributor (D) of the film, is ensured by the cooperation of the roller ( 34 ) of the action lever ( 33 ) of said fulcrum shaft ( 10 ) with a cam-function lever ( 37 ), horizontally fulcrumed with one end of a support ( 36 ) fixed to the frame of the machine and provided on the other end with a trigger and hook device ( 42, 142, 43, 44, 46 ) which when is actuated by said roller ( 34 ), deactivates and allows the lifting of the lever ( 37 ) thanks to elastic return means ( 47 ). Consequently to said lifting, the gripper closes and grasps the film from the distributor. During the opposite displacement run of the gripper from the distributor, a cam ( 35 ) fixed to the carriage with the gripper, co-operates with a lateral arm ( 40, 140 ) of said lever with the function of cam ( 37 ), and causes the lowering of this latter in the original position, with re-loading of the relative trigger and hook device.

The invention relates to functional and constructive improvements in the movable gripper for the machines intended to the packaging of products with stretchable film, described in the Italian patent 1.262.267, belonging to the same applicant, to which is made ample reference. In this type of machines, the packaging film is supplied by a fixed and horizontal distributor, comb shaped, usually placed under the horizontal rollers which fold under the product the last edge of the portion of the packaging film previously retained by said distributor, while the same product is translated to the discharge by a pusher installed on the posterior folder. Under this posterior folder is installed in oscillating manner, parallel to the same folder, a comb-shaped gripper, complementary to the combs of said distributor, which is oriented toward this latter with its teeth and which by suitable means can be opened or closed and can be carried from a horizontal, raised position, to a lowered and downwardly inclined position, and vice-versa. When the carriage with the posterior folder performs its approach run to the distributor, the gripper is initially in the raised position and is closed and then in correct phase is opened and downwardly inclined in such a manner to fit the teeth of the comb distributor which in correct phase has abandoned the last edge of the packaging film of the product being discharged and now is supporting the new head of the film which will envelope the following product. At the end of said run of the posterior folder, the gripper closes and grasps the head of the film supported and guided by the distributor. When the posterior folder performs the displacement run from the distributor, the gripper remains closed and initially in low position to extract the film from the distributor and then it is horizontally raised to be pre-arranged to the repetition of a new working cycle. In the gripper realised according to the known art, the lower jaw is pushed upwardly by a flat spring presenting difficult pre-loading, which causes undesired frictions and which results to be with a poor reliability. Object of the invention is to obviate to this drawback with the use of helical pin spring. Always in the gripper according to the known art, the opening oscillation movement of the lower jaw, is ensured by the co-operation of a lever keyed on the fulcrum shaft of the said jaw, with an oscillating cam pre-arranged on an axle parallel to the working run of the gripper and which is normally maintained in the vertical position by elastic means. When the said lever arrives in the final portion of the profile of said cam, it comes up against a recess step which makes the gripper to close on the film distributor and the end of the same lever is positioned on a laterally inclined portion of the cam, so that when the gripper is moved away from the distributor, the said lever causes the cam to oscillate around its own fulcrum and neutralise the same. This solution causes remarkable sliding frictions between the pin of the lever arm and the cam, makes the active positioning of the same cam unstable and it is not fitted for the speed and for the high working cycles of the packaging machine. The use of new cam means more reliable and without the sliding frictions of the known solution has obviate to these drawbacks. Always in the known art, the raising and lowering movement of the gripper is ensured by the co-operation of an extension beyond the fulcrum of the stem of the upper jaw of the same gripper, with a little and overhanging cam provided with two consecutive eccentricities, placed with an angular distance between them of about 30-45° and therefore with a steep and short fall between the two eccentricities. This solution causes concentrated and quick wears of the cam and it is not suitable for the speed and the high working cycles of the packaging machine. Besides, the gripper can freely upwardly oscillate. Object of the invention is to obviate to these drawbacks pre-arranging the gripper for the double-effect co-operation with opposite points of a single-eccentricity cam, and to act with this cam by means of rolling friction and to cause that this cam may be actuated with oscillations up to about 120-180° and with a gradual progression, not obtainable with the known means.

These and other features of the improvements which is referred to and the advantages deriving therefrom, will appear better evident from the following description of a preferred embodiment of the same, made by way of non-limiting example, with reference to the figures of the attached sheets of drawings, in which:

FIG. 1 is a plan view from the top and with portion in section of the gripper which is referred to, taken in the stretching end run position of the film in the packaging station;

FIG. 2 is a top view of the posterior and middle portion of the gripper connected to the opening-closing and lifting-lowering shafts of the same gripper;

FIGS. 3 and 4 are lateral views and with portions in section of the gripper respectively in the upper and closed position, when it arrives at the level of the opening means and at the end of the co-operation run with said opening means, when it stops to grip the film from the distributor and to begin the reverse translation run, to stretch a new portion of film in the packaging station.

In FIGS. 1 and 3, with numeral reference 1 is shown the carriage which carries the posterior folder, the pusher and the mobile gripper for the clamping of the film, which carriage has for example a flat conformation, is inferiorly ribbed, has a plant shape which is substantially rectangular and is provided at the ends with carriages with small wheels 2 which run in corresponding horizontal slots, not shown, fixed to the frame of the machine and parallel to the rectilinear actuator 3 visible in FIG. 3, driven by a step motor controlled by the computer of the machine and to the movable element of which is connected in a known manner the same carriage 1 which is referred to. With numeral references 4, 4′ there are shown the pairs of slide cams which run in corresponding horizontal guides, of known type, which act on the lateral grippers of the packaging machines and which are not further considered because unrelated to the understanding of the invention. The front of the carriage 1 which is turned in the discharging direction of the packaged product, is provided with a wide symmetrical recess 5 which is occupied by the flat and posterior folder 6, shown with dash and dot line of FIG. 1, fixed with screws 7 and made with any suitable and/or if required treated material in such a manner to have a low coefficient of friction with respect to the packaging film and whose anterior edge 106, which is conveniently projecting from the carriage 1 and which is parallel to this one, is suitably bevelled. The carriage 1 carries integral, under the folder 6 and in median position, a small raised wall 101 which is posteriorly ribbed, provided with a pair of through holes to which may be pressure coupled the connection appendices of a little rubber cap, downwardly open, which is partially surmounting the folder 6 and which acts like a yielding hold up or contrast means to posteriorly push the product during the finishing phase of the packaging and during the translation toward the discharging station of the machine.

The carriage 1 carries integrally, in middle position and projecting in a direction which is opposite to the folder 6, a small horizontal and annular appendix 201, whose lateral walls rotatably support with small bushings 9, a first shaft 10 which is horizontal and parallel to the anterior edge 106 of said folder. On the portion of the shaft 10 which is placed inside of the support ring 201, there are rotatably assembled, with small bushes 11, the lateral walls of the forked terminal end 112 of the stem 212 of the upper, ribbed and flat jaw 12 of the gripper P which is referred to, which jaw has in plan view a substantially rectangular shape and posteriorly is connected with a symmetrically tapered conformation to the stem 212 and is provided with a rectilinear anterior edge 312, having a rounded shape and which incorporates the anterior edge of the folder 6 when the gripper is raised.

The posterior fork 112 of the upper jaw 12 of the gripper P supports, with the interposition of eccentric bushes 13, the ends of a pivot 14 which is parallel to the shaft 10 and upon which there is rotatably assembled a bearing 15. Parallelly to the same shaft 10, the support ring 201 rotatably supports with the interposition of bushes 16 an end portion of the shaft 17 upon which there is keyed by means of the grub screw 18 an eccentric 19 made of suitable material, having a cylindrical shape, which co-operates on one side with an upper bar 112′ of the fork 112 and which with another portion which is substantially with an angle of 180° with respect to said bar, co-operates with the above mentioned bearing 15, the whole in such a manner that rotating the shaft 17, the eccentric 19 causes the lowering or the raising of the upper jaw of the gripper P, with a double control effect. The eccentric bushings 13 are provided with fixing radial grub screws 20, through which it is possible to ensure the better contact position of the bearing 15 with the eccentric 19, also in presence of possible working tolerances of the various portions which compose the gripper P. It is clear that the fork 112 is provided between the bar 112′ and the small support portion of the pin 14, with wide side grooves which avoid interference between the same fork and the shaft 17. Always from FIGS. 1 and 3 it is noted that the shaft 17 has a length which is sufficient to rotatably traverse one of the lateral cams 4′ of the carriage 1 and a small support 21 placed under said fix cam and fixed to said carriage 1 and on the end of the same shaft 17 is square-keyed a small lever 22 high oriented and in the direction of the folder 6 and which is carrying on its free end a lateral roller 23, the axis of which is parallel to the shaft 17. On the portion of the shaft 17 which runs between the cam 4′ and the support ring 201 there is wound a needle spring 24 which with its end 124 is anchored to a wall of the ring 201 of the carriage 1 and with the other end is anchored to a bush 25 fixed with a grub 26 on the same shaft 17. The spring 24 is pre-loaded in such a manner to maintain the lever 22 in resting against a lower retainer 121, integral with the support 21. In these conditions, the eccentric 19 is in the position of FIG. 3 and maintains the upper jaw of the gripper P raised against the folder 6.

Always from FIGS. 1, 2, and 3 it is noted that on the portion of the shaft 10 which is comprised between the lateral walls of the posterior fork 112 of the stem of the upper jaw 12, there is fixed with its structural clamp end 127, the stem 227 of the lower jaw 27 of the gripper P, comb-shaped and when it is in the closing position, touches with its teeth a strip 28 of material with a high coefficient of friction, for example rubber, fixed on the lower face of the upper jaw 12 of the same gripper P. The lower gripper 27 is normally urged in closure by a couple of needle springs 29, 29′ which wind around portions of the shaft 10 which are laterally projecting from the ring 201 of the carriage 1 and which are anchored with the external ends to bushings 30, 30′, fixed with grubs to the same shaft 10 and which with the other end are anchored with screws 31, 31′, with lateral ledges 412, 412′ of the said posterior fork 112 of the stem of the upper jaw, the same springs 29, 29′ being opportunely pre-loaded to urge the two jaws of the gripper P the one against the other, with an appropriate thrust. From FIG. 2 it appears how the posterior fork 112 is superiorly provided with a window 32 through which it is possible to act on the screw of the clamp 127 which fixes to the shaft 10 the stem of the lower jaw 27 of the gripper P. Through this window there projects an appendix 327 which is bent upwards, onto which the operator act to lower the inferior jaw 27 each time that this operation is required.

The shaft 10 passes in rotatable manner through one of the internal cams 4 integral with the carriage 1 and carries keyed at the end a lever 33 oriented in the same direction of the lever 22 and provided on its end with a lateral roller 34, the axis of which is parallel to the shaft 10. Laterally to the roller 34, on the carriage 1 there is fixed a cam 35 upwardly oriented, which will be discussed after.

The actuator 3 is placed on the side of the carriage 1 which carries said lever 33 and taking advantage of the lateral grooves 103 of the body of said actuator, upon this is laterally fixed a base 36 which carries the mechanisms described after to actuate the opening and then the closure of the described gripper when the carriage 1 reaches the expulsion end run of a packaged product and when the same gripper P arrives to co-operate with the known type distributor D, to clamp from this the new head of the film which must be stretched in the packaging station of the machine during the next return run of the same carriage 1.

From FIG. 3 it is noted that, when the carriage 1 reaches the position in which must begin the opening of the gripper P, the roller 34 of the lever 33 begins to co-operate with the inferior side of a lever 37 downwardly inclined, placed with its longitudinal axis on an ideal vertical plane which is parallel to the run of the carriage 1 and articulated with one end on a pin 38 fixed to the plate 36 and parallel to the shaft 10. On the same end of the fulcrum, the lever 37 carries laterally fixed, by means of the screws 39, a lever arm 40 downwardly oriented, in the opposite direction with respect to said lever 37 and which terminates with a rounded end 104 placed on the sliding path of the cam 35 fix to the carriage 1. When the lever 37 is in the active position of FIG. 3, the end 140 of the lever arm 40 is raised and does not interfere with said cam 35. The lever 37 carries on the end which is opposed to the one of the fulcrum, a laterally flattened portion 137, upon which is inter-fulcrumed at 41, parallel to the fulcrum 38, a short lever 42 which with a lower portion 142 inferiorly projects from said lever 37 to act as a trigger and which with an upper portion projects superiorly from said lever, to act as an harpoon, said upper end of the lever 42 being provided with an horizontal pin 43 which engages a lateral recess 44 of a small vertical guide 45 fixed upon the small plate 36. A return spring 46 is housed in a seat obtained on the base of the recess 137 of the lever 37 and acts on the upper arm of the lever 42, to maintain the small pin 43 inside of the recess 44, while a second return spring 47 is laterally anchored at 48 to the lever 37 and with the other end is anchored to an appendix 49 of the upper portion of the guide 45, at the level of which the same guide is provided with a projecting step 50 partially realised with elastic-yielding material. When the roller 34 of the lever 33 runs along the lower and descending side of the lever 37, the shaft 10 of the gripper oscillates in counterclockwise direction for who is seeing FIGS. 1 and 3 and the lower jaw 27 of the gripper P oscillates downwardly and moves away from the upper jaw 12, opening the same gripper. In correct phase with the above mentioned opening phase, the gripper P oscillates downwardly to reach the same level of the complementary gripper PD of the distributor D which retains the new head of the packaging film F. To this function provides a cam 51 fixed to the frame of the machine, against the vertical edge of which there arrives to co-operate the roller 23 of the lever 22, in such a manner that by effect of the translation of the carriage 1, said roller at first goes up on the front 151 of the cam, then goes down, then runs along the rounded corner zone 251 of the same cam and finally runs along the inferior and horizontal side of the same cam 51. As a consequence of this wide movement of the lever 22 and of the relative shaft 17, the eccentric 19 rotates in clockwise direction for who is seeing FIGS. 1 and 4 and the whole gripper P is lowered while remains opened and disposes with the upper jaw 12 and with the lower jaw 27 respectively over and under the gripper PD of the distributor D. When the carriage 1 is about to perform the last millimetres of its run toward the distributor D, the roller 34 of the lever 33 touches the lower trigger 142 of the lever 42 and compels said lever to rotate in clockwise direction for who is seeing FIG. 3, determining the disengagement of the pin 43 from the recess 44, in contrast with the spring 46, so that by effect of the traction performed by the spring 47, the lever 37 oscillates rapidly upwardly as from FIG. 4, causing the rising of the lower jaw 27 of the gripper P, the teeth of which pass through the empty spaces of the comb PD of the distributor and raise the head of the film F clamping the same firmly against the rubber strip 28 of the upper jaw 12. The pin 43 runs on the side of the guide 45 and arrives against the elastic rubber bumper 50. With the raising of the lever 37, the inferior side of said lever has been moved over the roller 34 of the lever 33, while the lever arm 40 has been lowered and its end 140 has been carried to the level of future co-operation with the cam 35. When the run of the carriage 1 is inverted and the gripper P moves away from the distributor, with a movement toward the right for who is seeing FIG. 4, the same gripper P remains closed and remains low to be whitdrawn from the gripper PD of the distributor D. When the roller 23 of the lever 22 is moving backwards the inferior side 351, then the corner zone 251 and then the front 151 of the cam 51, the gripper P has came out from the distributor D and gradually returns in the high position of FIG. 3, with the conclusion of its lifting when the roller 34 has gone beyond the fulcrum zone 38 of the lever 37, in such a manner that the gripper must change its disposition remaining always strictly closed. When the cam 35 passes under the end 140 of the lever 40, said lever is raised causing the lowering of the lever 37, while the lever 42 with the functions of hook and trigger is reloaded as from FIG. 3, preparing the whole mechanism for the repetition of a new working cycle. It is to be understood that the end 140 of the lever 40 may be provided with a roller for the co-operation with rolling friction with the cam 35. For the same objects, also the upper bar 112′ of the posterior fork 112 of the upper gripper, may be provided with a roller for the co-operation with rolling friction with the eccentric 19, even if said eccentric works preferably in contact with the lower bearing 15. 

1) Movable gripper for machines for the packaging of products with stretchable film, placed under the posterior folder (6), which, with the pusher (8) for the expulsion of the packaged product are assembled upon a same horizontal translation carriage (1), gripper of the type which comprises a flat and superior jaw (12), carried by a forked arm (112) inter-fulcrumed upon a shaft (10), which is horizontal and parallel to said carriage and rotatably supported by at least a pair of parallel supports (201) integral to the median and posterior portion of the same carriage, on the centerline of said shaft being fixed the end of the arm (127) which carries the lower jaw (27) of the same gripper which is referred to and the said shaft being provided at its end with a square lever (33) with a lateral appendix for the co-operation with the cam means for the opening and closing operations of the gripper (P) which can be maintained horizontal or may be lowered by the action of eccentric means keyed on a shaft (17) parallel to the one for the fulcrum of the gripper, rotatably supported by the same support (201) and which is provided at its end with a square lever (22) for the co-operation with cam means which encounters during the movement of the carriage, gripper of such a type characterised by the fact that said eccentric means (19) co-operate with opposite portions (112′, 15) provided on the posterior and forked portion of the stem of the upper jaw (12) of the gripper, the whole in such a manner to control with a double effect action the oscillation of the same gripper around the fulcrum shaft (10). 2) Gripper according to claim 1) characterised by the fact that said eccentric means (19) are constituted by a cylindrical and round section body (19) of suitable material, provided in eccentric position and parallelly to its axis with a hole traversed by the support shaft (17) upon which the same eccentric is fixed, for example, with a grub screw (18). 3) Gripper according to claim 1) characterised by the fact that the eccentric (19) superiorly co-operates with a bar (112′) integral to the posterior fork (112) of the arm of the upper jaw (12) which fork supports in contrast to said bar and with the interposition of regulation eccentric means (13, 20) a pin (14) parallel to the shaft (17) with the eccentric and upon which there is rotatably assembled a roller or bearing (15) which co-operates by rolling friction with the lower portion of the said eccentric (19). 4) Gripper according to claim 3), characterised by the fact that the bar (112′) which co-operates with the upper portion of the eccentric (19), rotatably supports a roller or another suitable co-operation mean with rolling friction with the same eccentric (19). 5) Gripper according to claim 1), characterised by the fact that the shaft (17) which carries the eccentric (19) is rotatably supported at the more distant end from the same eccentric, by means of a support (21) placed at the level of a side of the carriage (1) to which said support is fixed and on said end of the shaft which is projecting from said support, there is fixed a square lever (22) upwardly oriented and toward the anterior front of the gripper, provided at the end with a Jateral roller (23) and that when it is in its rest position is pushed by the action of the elastic means (24) resting on a lower retainer (122) integral with said support (21), the whole in such a manner that in said rest position, the eccentric (19) presents the major eccentricity downwardly oriented and the upper jaw (12) of the gripper results raised and in contact with the overhanging posterior folder (6). 6) Gripper according to claim 5) characterised by the fact that the elastic means (24) which contrast the rotation of the shaft (17) for the support of the eccentric (19) are constituted by a pre-loaded needle spring which is wound on a portion of said shaft, and also anchored with one end to a bush (25, 26) fixed on the same shaft and anchored with the other end to the posterior support (201) of the carriage which rotatably carries the same shaft (17) and the fulcrum shaft (10) of the same gripper (P) which is referred to. 7) Gripper according to claim 1), characterised by the fact that during the translation of the carriage (1) which carries the gripper, moving close to the distributor of the film, the end roller (23) of the lever (22) which controls the shaft with the eccentric (19), arrives to co-operate with the front (151) of a fixed cam (51) upon which front the same roller progressively goes up raising said lever in vertical position and then lowers while said lever continues in the backwards rotation, afterwards said roller co-operates with a corner zone (251) suitably bevelled of said cam and finally runs along the horizontal inferior side (351) of the same cam, while said lever (22) remains backwardly oriented, in the condition in which the eccentric (19) upwardly oriented with the major eccentricity and with the gripper downwardly oriented, in the correct position for the co-operation with the distributor D of the packaging film. 8) Gripper according to claim 1) characterised by the fact that the fulcrum shaft (10) of the jaws of the same gripper, projects with both ends from the small annular frame (201) for the support of the carriage (1) and on both projecting portions carries wound needle springs (29, 29′) suitably pre-loaded, which with one end are anchored to bushings (30, 30′) fixed to said shaft, while with the other end the said springs are anchored to portions (31, 31′, 312, 312′) fixed to the terminal fork portion of the arm (112) of the upper jaw (12), in such a manner that the two jaws of the gripper result to be pushed by said springs the one against the other, with a correct pressure. 9) Gripper according to claim 8) characterised by the fact that the square lever (33) fixed to the end of the fulcrum shaft (10) of the same gripper, is provided at the end with a lateral roller (34) parallel to said shaft and that during the translation of the carriage (1), when it is required that the gripper opens itself, runs along the lower side of a lever (37) downwardly oriented, fulcrumed with the upper end to an axis (38) which is integral to portions (36) fixed to the frame of the machine and parallel to said shaft, the lower end of said lever (37) being provided with a lateral recess (137) in which is constrained with interfulcrum (41) a small lever (42) which projects under the main lever with a portion (142) having the function of trigger, placed on the path of said roller (34) and which is superiorly projecting from said main lever with a portion having the function of an hook, provided with a lateral appendix (43) which by an elastic means (46) is pushed to engage a lateral recess (44) of a small vertical and fixed guide (45) and elastic means (47) to upwardly urge said lever (37) being provided, the whole in such a manner that when the said roller (34) co-operates with said inclined lever (37), the lower jaw of the gripper is moved away from the upper jaw and when the same gripper has arrived opened and in low position in co-operation with said gripper (PD) of the distributor (D) of the film, said roller (34) co-operates with the lower trigger (142) of the small lever (42) and causes the disengagement of the upper hook (43) of this one by the retaining step (44), so that said lever (37) with the function of cam, is raised by the action of said elastic means (47) and is arrested with the hook (43) against an elastic bumper (50), while the lower jaw (27) of the gripper is hastily raised and carries the head of the film retained by the comb of the film distributor (D), to be fixed between the teeth of said jaw (27), and a strip of rubber (28) of the upper jaw of the same gripper, means being provided to re-load in the downwardly inclined position said lever (37) with the function of cam, as soon as said roller (34) has gone beyond said lever during the displacement run of the gripper from the film distributor. 10) Gripper according to claim 9), characterised by the fact that the lever (37) with function of cam carries integral and laterally at its fulcrumed end, in a position which not interfere with the roller (34) and with the relative lever (33) of the opening and closing movement of the said gripper, a short lever arm (40) downwardly oriented, which ends with a rounded end (140) or provided with roller, with which is co-operating a cam (35) fixed to the carriage (1) which provides to the re-loading of said lever with the function of cam during the displacement run of the gripper from the film distributor. 